Solar Granules

Sunspot 2529 - Two Views

During the morning and afternoon of April 16th observing conditions were nearly perfect: clear sky, calm wind, temperature near 60 degrees, and decent seeing. My goal was to image significant sunspot 2529 in both hydrogen alpha and white light.

I began with the hydrogen alpha view. The first image below is an 8-panel mosaic of the Sun's western limb with sunspot 2529 nearby. Some modest prominences adorn the limb. (Click on the images for a larger view.)

The next image is a closer view of the sunspot showing detail in the dark umbra and white active areas near the spot.

Small sunspot 2532 had just emerged on the eastern limb where a spiky prominence can be seen in the next 4-panel mosaic.

Beautiful observing conditions continued into the afternoon, so I mounted my Stellarvue 130mm and tried white light imaging for the third time. Better seeing and better filters improved my results. The next image was my best effort. It was done using a Herschel wedge with a 5X Barlow lens combined with stacked neutral density and uv/ir filters. Detail in the umbra and penumbra is pretty good. Surface granulation is plainly visible, but not as sharp as the umbra detail. This is clearly superior to my previous white light images.

Since the sunspot was getting near the western limb on the right side of the image, the granules there are smeared out. Granule boundaries are sharpest in the center of the solar disc to the left.

I took an image of granules in the center of the disc where no sunspots existed so I could compare my image with an image of the same region taken by the Solar Dynamics Observatory orbiting above the atmosphere. My image is first below followed by the SDO image. I tried to get the image scales roughly equal.

The clarity and sharpness of the satellite image is obviously superior to my image, but I'm getting closer to respectability. My image also contains noticeable distortion in the lower corners. Perhaps I didn't quite get the center of the Sun, or, maybe, it's an optical distortion. I'll keep trying to home in on the correct combination of filters, exposures, and Barlow lenses.